Molecular systematics of Tetraplasandra, Munroidendron and Reynoldsia Sandwicensis (Araliaceae) and the evolution of superior ovaries in Tetraplasandra

Abstract

Systematic relationships within the Hawaiian group Tetraplasandra A. Gray, Munroidendron Sherff and Reynoldsia sandwicensis A. Gray are investigated here based on parsimony analysis of nucleotide sequences from the internal transcribed spacer (ITS 1 and 2) regions and the non-transcribed spacer of 5S (5S-NTS) nuclear ribosomal DNA. Results indicate that Tetraplasandra, Munroidendron and Reynoldsia sandwicensis form a single monophyletic group, and that Reynoldsia A. Gray is paraphyletic. Both data sets support combining Reynoldsia sandwicensis with Munroidendron and treating it as distinct from Reynoldsia species outside Hawaii. Both data sets support two major clades: a Munroidendron/Reynoldsia sandwicensis clade and a Tetraplasandra clade, but they are discordant in relation to the monophyly of Tetraplasandra. 5S-NTS results support treating Tetraplasandra, Munroidendron and Reynoldsia sandwicensis as a single genus, whereas ITS results suggest that Tetraplasandra represents a distinct genus from Reynoldsia sandwicensis and Munroidendron. Tetraplasandra gymnocarpa (Hillebr.) Sherff is the only member of the Araliaceae with a completely superior ovary, and in T. kavaiensis (H. Mann) Sherff the ovary is partially superior. Together, they form a well-supported clade within the Hawaiian complex, confirming the hypothesis that in Tetraplasandra superior ovaries evolved in Hawaii from an epigynous ancestor.